Venous System: Physiology of the Capacitance Vessels

Rothe, Carl F.

doi:10.1002/cphy.cp020313

Cited by 119 publications

(95 citation statements)

References 429 publications

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“…T 1/2 is the time that takes for half the leg blood volume to return to the central part of the body, whose properties are quite transient, and a function of time. These two physiological variables are greatly involved in the process of regulating cardiac performance and systemic arterial pressure [8,9]. Sympathetic reflex response was directly recorded as the muscle sympathetic nerve activity (MSNA) by a microneurographic technique.…”

Section: Age-related Influences Of Leg Vein Filling and Emptying On Bmentioning

confidence: 99%

Age-Related Influences of Leg Vein Filling and Emptying on Blood Volume Redistribution and Sympathetic Reflex during Lower Body Negative Pressure in Humans.

Iwase

Niimi

et al. 2002

JJP

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In aged people, decreases in stroke volume and cardiac output during orthostatic challenge were found to be reduced [1][2][3]. Although the exact mechanisms have not been well clarified, it is supposed that the stiffness of the vessels is greater in the elderly, blunting venous pooling in the legs and reducing the drop in central blood volume in an upright position [4].Olsen et al. [5] observed that baseline leg venous compliance was smaller, and the capacitance response in the legs to lower body negative pressure (LBNP) was lower in elderly people. They proposed that the decreased leg venous compliance with advancing age and the concomitant reduction in capacitance response during LBNP could have implications for both the sympathetic reflex and the cardiovascular responses during acute hypovolemic circulatory stress, which might be diminished in aged people. Their recent study suggested that the attenuated cardiovascular responsiveness found in the elderly during orthostasis seemed to be caused by a reduction in leg capacitance response and a concomitant smaller central hypovolemic stimulus rather than a reduced efficiency of the reflex response [6]. However, no work has been done to investigate simultaneously the venous system, Japanese Journal of Physiology, 52, 77-84, 2002 Key words: venous distensibility index, half-emptying time, muscle sympathetic nerve activity, gravitational stress. Abstract:To test the hypothesis that leg vein filling and emptying functions could be impaired with advancing age, which would produce less blood volume redistribution toward the lower body and smaller sympathetic reflex response during mild gravitational stress, 9 young and 10 elderly healthy males were exposed to a lower body negative pressure (LBNP) of 15 mmHg. Venous occlusion plethysmography was used to determine the functions of the leg veins. We found that the baseline venous distensibility index (VDI) was lower (0.057Ϯ0.004 vs. 0.048Ϯ 0.003 ml · 1 00 ml, young vs. elderly; pϽ0.05), and half-emptying time (T 1/2 ) was shorter (1.6Ϯ0.1 vs. 1.3Ϯ0.1 s, young vs. elderly; pϽ0.05) in the elderly. At 15 mmHg-LBNP, VDI was decreased and T 1/2 was shortened significantly in the young group, but only slightly in the elderly group. Neither blood pressure nor heart rate changed significantly in either group. The reduction in peripheral venous pressure, which was recorded from the left antecubital vein at the cubital fossa, was less in the elderly, indicating a smaller decrease in central blood volume during LBNP; however, the enhancement of muscle sympathetic nerve activity was nearly the same as that in the young. We conclude that leg vein filling and emptying functions are impaired in elderly people, producing less blood pooling in the legs and smaller reduction in peripheral venous pressure during LBNP; the maintained sympathetic reflex response might be attributable to the well-preserved baroreflex function control of sympathetic outflow to the muscle in the elderly.

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Section: Age-related Influences Of Leg Vein Filling and Emptying On Bmentioning

confidence: 99%

Age-Related Influences of Leg Vein Filling and Emptying on Blood Volume Redistribution and Sympathetic Reflex during Lower Body Negative Pressure in Humans.

Iwase

Niimi

et al. 2002

JJP

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“…The blood volume has been separated conceptually into an unstressed (Q 0 ) and a stressed (Q s ) volume [21] where Q 0 is the maximal volume of the vessel without stretching the vessel wall, i.e., without tension in the wall or pressure on the blood. It accounts for about 75 % of the total blood volume [20]. Q s represents the remaining 25%, necessary to generate a positive pressure within the blood vessels.…”

Section: Discussionmentioning

confidence: 99%

“…Changes in myocardial function will affect venous return through changes in P cv due to a change in transmural P cv if intrathoracic pressure is constant. The balance between venous return and cardiac function [9] has become general knowledge and can be found in many textbooks [20] and review papers. The aim of this study was to determine P sf , R sf , P cv and Q in the intact, anaesthetized pig before and during continuous endotoxin infusion and subsequent volume restoration and to analyse the characteristic changes in the circulatory system.…”

Section: Introductionmentioning

confidence: 99%

Effects of endotoxin infusion on mean systemic filling pressure and flow resistance to venous return

Hiesmayr

Jansen

Versprille

1996

Pfl�gers Archiv European Journal of Physiology

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Mean systemic filling pressure (P sf ) is an indicator of the filling state of the systemic circulation. Cardiac output (Q) is related linearly to the difference between P sf and central venous pressure (P cv ), according to: Q = (P sf 9 P cv )/R sf , where R sf is the flow resistance downstream from the sites where blood pressure is equal to P sf . In 16 anaesthetized pigs we evaluated P sf , R sf and Q during baseline conditions, continuous endotoxin infusion and after subsequent fluid loading. P sf and R sf were determined from simultaneous measurements of Q and P cv at seven levels of lung inflation. The following results were obtained. P sf was 8.1 ± 1.8 mm Hg (mean ± SD) during baseline conditions, increased after endotoxin infusion to 9.9 ± 3.2 mm Hg (P = 0.04) and remained the same after infusion of 18 ml · kg -1 of Ringer's lactate. R sf increased from 0.34 ± 0.07 to 0.80 ± 0.34 mm Hg · ml -1 · s by endotoxin and decreased after fluid infusion to 0.58 ± 0.14. Q changed inversely proportional to R sf (P = 0.001). R sf changes were highly correlated with the changes in total systemic flow resistance (R s ) (P < 0.001). Endotoxin caused haemoconcentration and a decrease in plasma volume. The stability of P sf during endotoxin infusion and after volume loading indicate that the stressed volume was well maintained and changes in blood volume are compensated by changes in nonstressed volume. The increase in R sf can be attributed to arteriolar vasoconstriction, venous vasoconstriction and haemoconcentration.

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“…For hydrostatic reasons, zones 1 and 2 are more likely to occur in nondependent parts of the lung. Furthermore, respiratory changes in the intraluminal pressure of alveolar capillaries tend to track changes in ITP 7 and thus to decrease more than does P A during a spontaneous inspiration and to increase less than does PA on inflation of the lung with positive pressure. Thus, any increase in lung volume, whether in the context of spontaneous [51] or mechanically assisted breathing [45], has the potential to promote the formation of zones 1 and 2 at the expense of zone 3, and thus to increase RV afterload.…”

Section: Rv Afterloadmentioning

confidence: 96%

Interactions between respiration and systemic hemodynamics. Part I: basic concepts

Feihl

Broccard

2012

Applied Physiology in Intensive Care Medicine 1

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The topic of cardiorespiratory interactions is of extreme importance to the practicing intensivist. It also has a reputation for being intellectually challenging, due in part to the enormous volume of relevant, at times contradictory literature. Another source of difficulty is the need to simultaneously consider the interrelated functioning of several organ systems (not necessarily limited to the heart and lung), in other words, to adopt a systemic (as opposed to analytic) point of view. We believe that the proper understanding of a few simple physiological concepts is of great help in organizing knowledge in this field. The first part of this review will be devoted to demonstrating this point. The second part, to be published in a coming issue of Intensive Care Medicine, will apply these concepts to clinical situations. We hope that this text will be of some use, especially to intensivists in training, to demystify a field that many find intimidating.

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Venous System: Physiology of the Capacitance Vessels

Cited by 119 publications

References 429 publications

Age-Related Influences of Leg Vein Filling and Emptying on Blood Volume Redistribution and Sympathetic Reflex during Lower Body Negative Pressure in Humans.

Age-Related Influences of Leg Vein Filling and Emptying on Blood Volume Redistribution and Sympathetic Reflex during Lower Body Negative Pressure in Humans.

Effects of endotoxin infusion on mean systemic filling pressure and flow resistance to venous return

Interactions between respiration and systemic hemodynamics. Part I: basic concepts

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